A small size reactor that effectively utilizes a space is provided. This reactor includes: a reactor body which includes a core and a coil attached to the core, a casing which houses therein the reactor body and which has an opening where a part of the reactor body protrudes outwardly, a bus bar which is a conductive component electrically connected to the coil and which covers a part of a side of the reactor body protruding from the opening, and a terminal stage which includes an extended portion formed of a resin material where a part of the bus bar is embedded and provided along an edge of the opening, and which supports an electrical connection portion between the bus bar and an exterior.